1. Field of the Invention
The present invention relates to a vehicle steering device and the like having a function of providing a steering assistance to steered wheels so that a vehicle travels while following a set target travel line.
2. Description of the Related Art
As a related-art vehicle steering device having a lane keeping assistance function, in Japanese Patent Application Laid-open No. 2001-001921, there is disclosed a vehicle steering device configured so that, when a steering assistance section is controlled so that an estimated travel locus approaches a target locus set based on a travel path shape of the vehicle, a control gain for controlling the travel locus to approach the target locus is corrected based on a curvature.
This related-art device corrects the control gain for controlling the travel locus to approach the target locus based on the detected curvature, and hence provides such an effect that the control gain for controlling the travel locus to approach the target locus is corrected based on the curvature of the vehicle travel path to prevent a driver from feeling a sense of discomfort during a trace of a travel line.
However, in the device described in Japanese Patent Application Laid-open No. 2001-001921, there is disclosed only a method of multiplying a future lateral deviation by the control gain for control torque setting for the steering assistance section, and it is not clear that the travel locus converges to the target locus. Moreover, for example, there is no description of a yaw rate of the vehicle, and the yaw rate is not considered. As a result, the travel along the target travel line may not be achieved.